Color photography and color photograph



Aug. 12, 1941. H. VERKINDEREN 2,251,965

COLOR PHOTOGRAPHY AND COLOR PHOTOGRAPH l Fi1ed March 11, 1938 f/'X /ucComponen f ase from, 1 7 f/gif Z0 l/mdalwf g'gglgnage Zig/zi and Developof rea/2 bmw/:m fo Yellow /ae-67ee/z /ma e uppar Yellow /magfe 35x 05e/rrau haai p g Wiege/zia /mage Patented Aug. 12, 1941 COLOR PHOTOGRAPHYAND COLOR PHOTOGRAPH Honor verhinderen, Mortsel, near Antwerp, Belgium,assignor to Gevaert Photo-Producten, N. V., Dude-God, near Antwerp,Belgium Application March 11, 1938, Serial No. 195,386 In Austria March30, 1937 2 Claims.

This invention relates to color photography.

The invention has for its object an improvement in color photography andconsists in a method which through color development enables adilTerently colored image to be produced in each of the separateemulsion layers of a multilayer photographic material.

Different methods of producing differently colored images by colordevelopment in the different emulsion layers of a multilayerphotographic material have already been proposed.

One of these methods consists in this, that to each emulsion layer -adierent dye component is added, which for each individual layer produceswith the oxidation products of one and the same developer the ldesiredcolor. This method has on the one hand the advantage, that with a singledevelopment the different color images are produced in all emulsionlayers, and on the other hand very great disadvantages, namely:20

thechoice of the dyes is limited, owing to the fact that the diierentcolors have to be produced with the oxidation products of one and thesame developer: the dyestuii components added to the emulsion have adetrimental effect on the durability of the emulsion; iinally the fixingof the dyestu components in the different emulsion layers so that theywill not wander from one layer into the other is a problem which isdiicult to solve.

Another known method consists in this, that each layer is developedseparately by means of a suit-able developer, to which a suitable dyecomponent is added. For carrying this into effeet the so-calledcontrolled penetration Ol the baths into lthe superposed emulsion layersis employed. According to this method, certain chemicals, which greatlyretard the penetration of the Abaths in the emulsion layers, are addedto the baths, the penetration of which it is desired to control. As soonas the bath has penetrated to the bottom of the layer to be treated, theaction of the bath is checked, so that it is thus possible 'to operateseparately on each layer. The practical application of the controlledpenetration of the baths is however very complicated and requires a veryexact and difficult control. Moreover, the treatment of a lm by thismethod takes much time, as before each treatment, in which thepenetration of the bath is to be controlled, the film has to be dried.

According to the invention eachlemulsion layer of a multilayer materialis also developed with the desired developer, to which a suitable dyecomponent is added. For enabling each indi- 50 sharp one.

., after exposure, is developed to the desired color,

this being done before the exposure and development of another layer.The separate exposure of each l-ayer is carried out by a method whichmight be called the controlled penetration of light.

The method is based on the phenomena now to be described:

If an emulsion layer be exposed to ordinary light and then developed andif a microscopic cross-section be thereupon made through the ayer thusdeveloped, it wm be found, that the boundary in depth between the zonewithout developed silver and the Zone with developed silver is notsharp, but that there is a transitory transition, namely from the zonewhere the density of the emulsion has reached its maximum towards thezone where no silver is present. If ithis experiment be carried out witha multilayer material, the emulsion layers of which possessapproximately the same sensitivity and the same sensitiveness to color,the undermost l-ayers will,

with increasing exposure, exhibit a rather high degree density longbefore the uppermost layer has reached its maximum density. In this casea micro cross-section will show that the uppermost silver grains of thelower emulsion layers are already capable of being developed long beforethe lowermost silver grains of the upper emulsion layer become capableof being developed. This is to be explained by the fact that theuppel'most silver grains of an emulsion layer are always more sensitivethan the undermost silver grains of the same emulsion layer.

The result is entirely different, however, when the emulsion layer,ihstead of being exposed to ordinary light, is exposed to a light whichis strongly absorbed by the emulsion l-ayer. If a gelatine emulsionlayer be exposed for instance to short wave ultra-Violet light, a lightwhich, as is Well known, is strongly absorbed by the gelatine, it willbe found, on a microscopic crosssection of the developed material, beingmade, that the boundary in depth between the zone Where all the silvergrains and the zone where no silver grains have been developed is a veryThis boundary is all the sharper, the more thoroughly the light used isabsorbed by the emulsion layer. Thus, when the exposure is made to shortWave ultra-violet light, the boundary between the zone showing themaximum density and the zone showing no blackening the emulsion adyestufr which strongly absorbs the light with the wave-length employed.The same effect may be obtained, if the exposure be made for instance toblue light, and the emulsion be dyed yellow before the exposure.

By exposing the film to a light which is sufflclently absorbed by theemulsion it is therefore possible, by correctly adjusting the exposure,selectivelyto regulate the depth of penetration of the light into theemulsion layer. It has been found, that for a definite intensity ofillumination and for a denitely strong absorption capacity of' theemulsion for the light used for expesare the possibility of penetrationof the emulsion layer by the light is limited and, with suf= ficientlylong periods of exposure, becomes independent of the duration ofexposure.

If exposure to a light which is suilciently strongly absorbed by theemulsion layers be employed with a multilayer film, it is possible, witha correctly adjusted exposure, to limit the developability of thelight-sensitive layers to one or to several layers. This can be besteffected if the exposure be made from the rear side, for the very reasonthat, as already stated above, the uppermost silver grains of anemulsion layer are always more sensitive than the lowermost silvergrains.

The process according to the invention is based on the phenomenon justdescribed and consists furthermore in this, that in the first place oneof the outer emulsion layers of a multilayer material, either the top orthe bottom emulsion layer, is separately exposed to a light which isstrongly absorbed by the emulsion, that the emulsion layer thus exposedis thereupon de veloped with a color developer which produces a coloredimage in the desired color and that finally the emulsion layer whichfollows the developed layer or the other outer emulsion layer is in thesame way separately exposed and developed with a suitable colordeveloper and the further layers are treated successively in the sameway. The remaining last layer may of course be exposed to ordinary lightwhich is not absorbed by the emulsion.

In order to explain the process a description is given below of the modeof operation with reference to the accompanying drawing, showing a flowdiagram of the operations, according to which an image in natural colorsis obtained on a three-layer material. It is of course to be understoodthat the invention is not limited to this mode of operation, but thatthe invention comprises all modes of operation in which one or morelight-sensitive layers of a multi-layer material are exposed separatelyto a light which is strongly absorbed by the emulsion layers.

The three-layer material for instance, which is used for the productionof images in natural colors, is of the known type. On a support thefollowing layers are coated, one over the other: an emulsion layersensitised for red; a gelatine layer which may contain a red filteringdyestuf; an emulsion layer sensitised for green; a gelatine layer whichmay contain a yellow filtering dyestui; finally an emulsion layer whichis not sensitised and is therefore only sensitive to blue. The yellowfiltering dyestuf may alternatively be added to the uppermost emulsionlayer instead of to the underlaying Gelatine layer. Although thegelatine layers Vbetween the various emulsions are not indispensable,their presence is of advantage, They offer great advantages for thereason that they make it possible, when the individual light-sentitivelayers are separately exposed, to employ a more thorough exposure andthus make allowance for the differences in thickness of the layers.

The three-layer material is exposed in an ordinary photographic orcinematographic camera; through the exposure a latent image is formed,viz. by the blue rays in the upper, the green rays in the intermediateand the red rays in the lower light-sensitive layer. After exposure inthe camera the three-layer material is developed in an ordinarydeveloper and thoroughly fixed. In this way three images are produced,one in each emulsion layer. 'I'he silver developed in the three layersis then reconverted by one of the known methods into light-sensitivehalogen silver, whereupon each' halogen silver image is separatelydeveloped to a color image of deinite color. The procedure is forinstance such that the lower emulsion layer is exposed from the back ofthe film to short wave ultra-Violet light, this exposure being soadjusted according to intensity and duration that the layer is rendereddevelopable through and through, whereas the other two layers remainundevelopable. The material exposed in this manner is thereupondeveloped with a color developer which develops the halogen silver imagein the lower layer and gives a blue-green color image. A suitabledeveloper is, for instance:

Formula 1 Dimethyl-p-phenylendiamine g-- 0.70 Sodiumsulphite, cryst g--10.00 Sodiunicarbonate, anhydr g-- 20.00 Water e ccm-- 1000.00a-Naphthol g 0.80 Methylalcohol ccm 100.00

When the film has been washed after development, it is treated for twominutes in a bath of tartrazine solution, The upper emulsion layer isthen exposed from above to short wave ultraviolet light. The intensityof' exposure and the concentration of the tartrazine solution areregulated in such a manner that the penetration of the light remainslimited to the upper emulsion layer which is itself rendered developablethrough and through. After this exposure the material is developed in acolor developer which develops the halogen silver image in the upperlayer and gives a yellow color image. A suitable developer is, forinstance:

Formula 2 Dimethyl-p-phenylendiamine g-- 0.80 Sodiumsulphlte, cryst g10.00 Sodiumcarbonate, anhydr g-- 20.00 Water ccm-- 1000.00Acetoacetanilide g-- 0.80 Isopropylalcohol ccm 100.00

After development the film is exposed to white light and exposed throughand through, whereby the halogen silver image in the middle layer aswell is rendered developable; after this exposure the material isdeveloped in a color developer which develops the halogen silver imagein the middle layer and gives a magenta color image. A suitabledeveloper is, for instance:

Formula 3 Dimethyl-p-phenylendiamine g 0.70 Sodiumsulphite, cryst g10.0.0 Sodiumcarbonate, anhydr g 20.00 Water com 1000.00'p-Nitrobenzylcyanide g-- 0.80 Acetone com 30.00 Isopropylalcohol ,ccm70.00

After in this way the desired color image has been formed in eachemulsion layer, the metallic silver is removed from the material, forinstance by Farmers reducer. A negative color image is obtained, inwhich the images consist exclusively of color gelatine. If such anegative lm be printed on a similar three-layer material and thismaterial be treated by the process described above, a positive colorimage in natural colors is finally obtained. p

The process described above may of course be modified in many ways.Thus, for instance, after exposing and developing the lower layer, thereduced silver may be removed from this layer and thereupon thethree-layer material be dyed a diffused yellow by immersion in a 5%solution of tartrazine. The so-treated threelayer material may then beexposed again from the reverse side, for instance with `dark blue lightwhich is not absorbed by the color image in the lower layer, but isabsorbed by yellow dyestuff which enters the material, owing to itstreatment in the bath of tartrazine solution. The length of exposure maybe so regulated that the light illuminates the middle layer through andthrough and renders it developable, without the upper layer beingrendered developable. The halogen silver image in the middle layer maythen be developed with the developer already given under Formula 3 to amagenta color image, whereupon the material may be exposed to whitelight and the halogen silver image in the upper layer developed to ayellow color image by means of the developer according to Formula 2.

Instead of the material which is exposed in a camera being developed toa negative image, the material may be developedl directly to a positiveimage, namely by the known reversal method. For this purpose thematerial, after being exposed in the camera, is first developed,whereupon the reduced silver is removed from the material, for instanceby means of an acid solution of sodium permanganate. A positive halogensilver image will thus remain in each layer. Each of these halogensilver images may be developed by the processes already described to acolor image .of the desired color, so that, aft-er remova1 of the silverreduced during the color development, a positive image in natural colorsis left.

I claim:

1. A method of producing a composite threecolor image on a photographicmaterial consisting of a support coated with three superposed,

differentially color-sensitive emulsion layers having a latent image ofa color component of said color image in each of said layers whichcomprises converting the latent image in each of said layers into acorresponding light-sensitive silver salt image, said layers beingotherwise undifferentiated, exposing one side of said material toshort-wave, ultra-violet light which is strongly absorbed by the gelatinof said emulsion layers independently of the presence of any other lightabsorbent and selected as to intensity to be substantially whollyabsorbed by said gelatin of the outer emulsion layer on the exposed sideof the material whereby the silver salt image in said layer is convertedinto a corresponding latent image without substantially affeecting thesilver salt image in the layer below it, developing the latent imageformed by said exposure to a corresponding color image, thereafterexposing the other side of said material to short-wave, ultravioletlight which is strongly absorbed by the gelatin of said emulsion layersindependently of the presence of any other light absorbent and selectedas to intensity to be substantially wholly absorbed by said gelatin ofthe outer emulsion layer on the second exposed side of the materialwhereby the silver salt image in said layer is converted into acorresponding latent image without substantially affecting the silversalt image in the layer below it, developing the latent image formed bysaid second exposure to a corresponding color image, and thereafterexposing the intermediate emulsion layer to light which will penetratesaid imtermediate layer through one of said outer layers and developingthe latent image thereby formed to a corresponding color image.

2. A method of producing a composite threecolor image on a photographicmaterial consisting of a support coated with three superposed emulsionlayers containing in each of said layers a light-sensitive silver saltimage corresponding to a dilerent color component of said color image,said layers being otherwise undifferentiated, which comprises exposingone side of said material to short-wave, ultra-violet light which isstrongly absorbed by the gelatin of said emulsion layers independentlyof the presence of any other light absorbent and selected as tointensity to be substantially Wholly absorbed by the gelatin of theouter emulsion layer on the exposed side of the material whereby thesilver salt image in said layer is converted into a corresponding latentimage without substantially affecting the silver salt image in the layerbelow it, treating the material with a color developing solution adaptedto convert the latent image formed in said outer layer by said exposureto a corresponding color image, thereafter exposing the other side ofsaid material to short-wave, ultra-l violet light Which is stronglyabsorbed by the gelatin of said emulsion layers independently of thepresence of any other light absorbent and selected as to intensity to besubstantially wholly absorbed by the gelatin of the outer emulsion layeron the second exposed side of the material whereby the silver salt imagein said layer is converted into a corresponding latent image withoutsubstantially affecting the silver salt image in the layer below it,treating the material with a second color developing solution adapted toconvert the latent image formed in said second outer layer by saidsecond exposure to a corresponding color image differing in color fromsaid first color image, and thereafter exposing the intermediateemulsion layer to light which will penetrate said intermediate layerthrough one of said outer layers and treating the material with a thirdcolor developing solution adapted to convert the latent image formed insaid intermediate layer by said third exposure to a corresponding colorimage diiering in color from both said rst and said second color images.

HoNoR VERKINDEREN.

